In electronic equipment, it is known to provide a plurality of power supplies for supplying various electrical loads (parts of the equipment) with different supply voltages. For example, the equipment may comprise communications or computing equipment in the form of circuit cards which are inserted into card slots in an equipment rack and are connected to, and interconnected by, a backplane. The equipment rack or an equipment frame may include one or more power sources which provide power to the circuit cards, for example in the form of a (nominally) 48-volt supply.
On each circuit card, this 48-volt input supply voltage may be converted into a plurality of individual supply voltages for different parts of the equipment on the card, by respective power supplies. For thermal and efficiency reasons, each power supply may be a switch mode power supply (SMPS) or DC power converter, but other forms of power supply, such as voltage regulator modules (VRMs), may also be provided. For example, the individual supply voltages may range from 1.5 volts or less to 5 volts or more. Each SMPS may conveniently, but need not necessarily, provide electrical isolation of its output voltage from the input supply voltage.
The various parts of the electrical equipment on such a circuit card increasingly may require that the individual supply voltages be applied and removed in a particular sequence or manner to avoid any possible damage to the equipment. In addition, monitoring of the individual supply voltages is generally required in order to ensure proper operation of the equipment and to detect power supply faults. Accordingly, it is known to provide a power supply controller or sequencer which performs these functions for the plurality of power supplies.
For example, one such power supply controller is known from “Modular Solid-State Power Sequencing”, Goodew et al., IBM Technical Disclosure Bulletin Vol. 15, No. 12, pages 3697-3699, May 1973. Another power supply controller, for two power supply channels or voltages, is provided by the LTC®1645 integrated circuit device as described in “LTC1645 Dual-Channel Hot Swap Controller/Power Sequencer”, Linear Technology Corporation, 1999. The latter device is intended to facilitate safe circuit card insertion in and removal from a live backplane, this being referred to as hot swapping of the circuit card.
However, hot swapping of circuit cards presents potential problems which are not addressed by the above controllers. For example, on insertion of a circuit card into a live backplane, to avoid undesired states (e.g. latch-up) of parts of the equipment on the circuit card it may be advantageous or necessary for a power supply controller on the circuit card to be powered up and operating before the circuit card is completely inserted to make signal connections. This can be facilitated using staggered connectors on the circuit card, but this still requires a rapid start-up of the power supply controller, for example within a few milliseconds.
In particular, it is generally desirable or necessary to ensure that the power supply controller is powered up and operating effectively (e.g. has completed its own start-up processes) to control the power supplies before the power supplies are themselves powered up, even though the power supply controller and the power supplies both derive their operating power from the same source.
In addition, the power supply controllers referred to above are limited in their applications. For example, neither of them is arranged to maintain, in arbitrary power supply arrangements, electrical isolation that may be provided between the input supply voltage and the output voltages of isolating power supplies.
A need exists to provide a power supply controller for controlling relatively arbitrary numbers and types of power supplies from various manufacturers, the power supplies providing various supply voltages from a relatively arbitrary input supply voltage, with any of various sequencing, monitoring, and control functions that may be desired in particular applications.